JPH09108717A - Clearance setting method for antifriction bearing of backup roll in rolling mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To greatly prolong the life of backup roll bearings and to improve the rolling precision of a steel strip by setting with a specific formula the clear ance of antifriction bearings of a backup roll in a rolling mill. SOLUTION: The clearance of antifriction bearings is properly set under the following formula for the backup roll of a rolling mill. CP= K.(Vn.L.WL.υ)<a> .Db <b> .e×P [-1/ L.NP.(Q/DP)<ab> }], assuming that K=10<6> to 10<7> , a=1/3 to 2/3, b=4/3 to 5/3, Cp: set clearance (μm), K: correction constant, Vn: number of rolling revolution (rpm), L: bearing width (mm), WL: rolling load (t), υ: lubricant viscosity (cst), Db : average diameter of bearings (mm), Q: cooling water flow rate (1/min), DP: cooling piping diameter (mm), NP: number of holes in cooling piping (pcs), and a, b: coefficient by bearing material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting a clearance for a backup roll rolling bearing of a rolling mill. In particular, the present invention relates to a setting method suitable for setting a clearance between the roller of the oil mist lubricated roller bearing and the outer circumference of the bearing inner ring.

[0002]

2. Description of the Related Art For example, a process line in which a continuous heat treatment facility and a rolling mill are provided in series, the rolled steel strip is heat-treated to impart workability, and then the shape of the steel strip is corrected by rolling to obtain a product. The rolling speed of is about 800 m / min or more for rolling the steel strip at high speed, so the rolling bearing of the backup roll that backs up the work roll of the rolling mill is
The total rolling load is applied and heat is generated due to the agitation resistance of the bearing lubricating oil during high-speed rolling. Particularly, in the case of dry rolling without using rolling oil, the bearing may be seized due to oil film breakage due to high temperature. Further, when the lubrication method of the bearing is changed from the conventional mogoyle lubrication to the oil mist lubrication in order to improve the rolling accuracy, the problem of heat generation in this bearing becomes particularly remarkable. Thus, in order to prevent seizure of the backup roll bearing, water cooling of the entire circumference of the roll chock is disclosed in Japanese Utility Model Laid-Open No. 61-53002.

[0003]

As described above, when the bearing inside is cooled by water cooling through the roll chock, the clearance (clearance) of the bearing is a combination of various thermal deformations, and its setting conditions are complicated. Is. That is,
The bearing lubricating oil is agitated by the high speed rotation of the rolls to generate heat, and it is extremely difficult to understand (estimate) the relationship between the thermal expansion of the bearing inner ring due to the heat generation and the heat shrinkage rate of the outer ring due to roll chock cooling. It was difficult to properly set the clearance of the rolling bearing. In this way, when the clearance of the rolling bearing of the backup roll is narrower than appropriate, the outer ring of the bearing clamps the inner ring of the bearing by sandwiching the roller, which causes spalling of the outer shaft of the bearing early and requires replacement. The operating rate of the rolling mill is reduced. If the rolling bearing clearance is wider than the appropriate value,
There is a problem that it becomes difficult to apply an accurate rolling load to the rolled steel strip due to the oscillation of the bearing inner ring, and high precision rolling becomes impossible. The method of the present invention has been made in order to advantageously solve such a problem, and provides a method for appropriately setting the gap of a backup roll rolling bearing of a rolling mill (in particular, an oil mist lubricated rolling bearing). It is intended.

[0004]

A feature of the method of the present invention is that the gap of the backup roll rolling bearing of the rolling mill is set based on the following mathematical formula, and the gap of the backup roll rolling bearing of the rolling mill is set. Setting method. Cp ＝ K ・ (Vn ・ L ・ W _L・ ν) ^a・ D _b ^b・ exp [−1
_{/ {L · N p · (} Q / D p) ab}] where ^{K = 10 6 ~10 7, a} = 1/3 ~2 / 3, b = 4/3 ~5 / 3 Cp: setting gap, K : Correction constant, Vn: Shaft speed, L: Bearing width,
W _L : Bearing load, ν: Lubricating oil viscosity, D _b : Bearing average diameter, Q: Cooling water flow rate, Dp: Cooling pipe hole diameter, Np: Number of cooling pipe holes, a, b: Coefficients depending on bearing material.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the method of the present invention will be described with reference to the drawings. In FIG. 1, a steel strip 1 is attached to an upper work roll 2,
Lower work roll 2a, upper intermediate roll 3, lower intermediate roll 3
a, upper backup roll 4, lower backup roll 4
In the 6Hi rolling mill 5 consisting of a, the upper and lower backup roll chock 6, 6a
A rolling load is applied to a, and continuous annealing (heat treatment) is performed by the upper and lower work rolls 2 and 2a through the upper and lower intermediate rolls 3 and 3a.
Continuous rolling is performed by applying a rolling load to the steel strip 1 after the heat treatment with equipment (not shown). As shown in FIG. 2, the backup rolls 4 and 4a of the rolling mill 5 have rollers 8 arranged on the bearing outer ring 7 with respect to the upper and lower backup roll chocks 6 and 6a, and the rollers 8 and the bearing inner ring outer circumference 9a (solid line). The gap 10 between and is set as follows. The bearing inner ring outer circumference 9a is the position of the bearing inner ring outer circumference 9a when the rolling load of the backup roll is being applied (during rolling).
b (two-dot chain line) is the position of the outer circumference of the bearing inner ring when the backup roll is unloaded.

The above-mentioned set gap is set in a range in which the life of the bearing outer ring 7 and the risk of seizure of the roller 8 are balanced, and it has been found from the actual measurement data that the proper gap is set by the above mathematical formula. It is a thing. As the actual measurement data, for example, cooling water temperature ≤50 ° C, outside air temperature ≤50 ° C
in the case of. Shaft speed _Vu = 374 (rpm), bearing average diameter _Db =
750 (mm), bearing width L = 400 (mm), bearing load W _L = (rolling load) / 2 = 600 (t), cooling water amount Q = 40 (l / min), lubricating oil viscosity at 40 ° C ν = 460 (cst), cooling pipe hole diameter D _p = 40 (m
m), when the coolant pipe Bolt N _p = 8 of (the), set gap Cp
= 500 (μm), the bearing outer ring life can be rolled by 500,000 tons or more. At this time, the values of the coefficients a and b depending on the bearing material in the bearing clearance setting formula according to the method of the present invention were a = 1/2 and b = 1527.

Next, the backup roll chock 6 in which the gap between the roller 8 and the bearing inner ring outer circumference 9a is set as described above.
As a result, when a rolling load is applied to the backup roll 4, as shown in FIG. 2, the bearing inner ring outer periphery 9a (solid line) comes into contact rotation in the angle θ range as a part of the roller 8 of the bearing outer ring 7 in the upper and lower roll chocks 6 and 6a. Then, the roller 8 at the θ portion generates heat due to friction and resistance to stirring of the lubricating oil to reach a high temperature, and seizure occurs. On the other hand, the roller 8 which is not in contact with the outer circumference 9a of the bearing inner ring has almost no heat generation and has a heat transfer level, which is lower than that of the θ portion.

Therefore, by cooling only the bearing outer ring 7 of the upper and lower roll chocks 6, 6a within the range where the contact rotation of the rollers 8 occurs, the bearing outer ring 7 of the upper and lower roll chock 6, 6a contacting the bearing outer ring 7 is rotated. Then, only the roller 8 having a high temperature is cooled to prevent seizure, and the bearing outer ring 7 of the bearing inner ring outer periphery 9a (solid line) is not contacted.
By reducing the temperature difference between the roller 8 and the roller 8, the heat distortion of the entire circumference of the bearing outer ring 7 is eliminated, and the roller 8 and the outer circumference 9 of the bearing inner ring are eliminated.
Rolling can be performed while maintaining the gap 10 with a at the set gap.

As a mechanism for performing such cooling, for example, as shown in the figure, a cooling pipe 11 is provided in the roll chock 6a near the bearing outer ring 7 in the range where the contact rotation of the roller 8 occurs, and the cooling pipe 11 is cooled. The bearing outer ring 7 can be cooled through the medium, and water (normal temperature) is optimal as the cooling medium. The cooling temperature of the bearing outer ring 7 to be cooled in this way is slightly different depending on the material of the roller 8 and the like, but if the material is a commonly used material, the material hardness of the bearing outer ring 7 can be reduced by cooling to 120 ° C. or less. It is possible to prevent the oil film from being broken due to a decrease in the viscosity of the lubricating oil at a high temperature, and to prevent the oil film from being broken. As a lower limit, it is possible to cool to the limit that can be cooled by water cooling.

By cooling the bearing outer ring 7 in this manner, seizure of the roller 8 is prevented, and thermal distortion of the entire circumference of the bearing outer ring 7 is eliminated, so that the roller 8 and the outer circumference 9 of the bearing inner ring are removed.
Rolling can be performed while maintaining the gap 10 with a at the set gap, and the steel strip can be rolled with high accuracy.

[0011]

EXAMPLES Next, examples of the method of the present invention will be given together with comparative examples.

[Table 1]

Note 1: The clearance between the inner ring of the bearing and the roller was set based on the above formula. Note 2: Rolling is a continuous process line consisting of continuous annealing equipment and temper rolling mill, and ultra low carbon steel strip after annealing (sheet thickness 0.6
mm, plate width 1000 mm) was continuously rolled as described above. Note 3: BUR diameter of rolling roll is backup roll, BU
The R axis is the backup roll axis diameter, the IMR diameter is the intermediate roll diameter, and the WR diameter is the work roll diameter. Note 4: The cooling range is the ratio of the contact rotation generation range of the roller to the entire circumference of the roll chock. Note 5: The set clearance is the clearance between the outer circumference of the bearing inner ring and the roller. Note 6: Outer ring bearing life is ○: rolled 500,000 t or more, △: rolled 100,000 to less than 500,000 t, ×: rolled less than 100,000 t. Note 7: Rolling accuracy is good: less than ± 0.001mm of target rolling thickness, no: more than ± 0.001mm of target rolling thickness.

[0013]

According to the method of the present invention, the life of the backup roll bearing can be remarkably extended, the operating rate of the rolling mill can be prevented from lowering due to the replacement of the bearing outer ring, and the productivity can be improved. In addition, the life of the bearing outer ring can be extended, and the repair cost can be significantly reduced. Further, it is possible to obtain an excellent effect that the rolling accuracy of the steel strip can be improved.

[Brief description of the drawings]

FIG. 1 is a side view showing an outline of a rolling mill.

FIG. 2 is a front view of a main part of a backup roll bearing portion.

Claims (1)

[Claims] 1. A gap setting method for a backup roll rolling bearing of a rolling mill, wherein the gap of the backup roll rolling bearing of the rolling mill is set based on the following formula. Cp ＝ K ・ (Vn ・ L ・ W _L・ ν) ^a・ D _b ^b・ exp [−1
_{/ {L · N p · (} Q / D p) ab}] where ^{K = 10 6 ~10 7, a} = 1/3 ~2 / 3, b = 4/3 ~5 / 3 Cp: setting gap, K : Correction constant, Vn: Shaft speed, L: Bearing width,
W _L : Bearing load, ν: Lubricating oil viscosity, D _b : Bearing average diameter, Q: Cooling water flow rate, Dp: Cooling pipe hole diameter, Np: Number of cooling pipe holes, a, b: Coefficients depending on bearing material.